CHAAC I+N+C - Blog

Performance Path vs Prescriptive Path in Title 24 Compliance (2026 Guide)

Tue, 24 Feb 2026 18:27:44 GMT

California’s Title 24 Building Energy Efficiency Standards (Part 6) establish mandatory energy requirements for residential and nonresidential buildings. After meeting required Mandatory Measures, projects must demonstrate compliance using either the Prescriptive Path or the Performance Path.

Understanding the difference between these two approaches is critical for architects, developers, engineers, and homeowners seeking permit approval while maintaining design flexibility and cost control.

What Is the Prescriptive Path?

The Prescriptive Path follows a fixed checklist of minimum efficiency requirements defined by climate zone and building type. Each component must independently meet specific thresholds, including:

Minimum insulation R-values
Maximum window U-factor and SHGC limits
HVAC equipment efficiency ratings
Lighting power density requirements

If every component complies exactly with the prescribed tables, no whole-building energy modeling is required. However, this method limits flexibility. If even one component fails to meet prescriptive criteria, the project must shift to the Performance Path.

What Is the Performance Path?

The Performance Path uses approved California Energy Commission software to simulate the building’s projected annual energy consumption and compare it against a code-defined baseline building.

Rather than requiring every component to meet a rigid checklist, this method evaluates the building holistically. Designers can trade efficiency between systems. For example:

Higher-performance glazing can offset slightly lower insulation values
Efficient HVAC systems can balance envelope trade-offs
On-site renewables may improve overall compliance margins

As long as the modeled building performs at or below the allowed energy budget, it complies.

What Does Performance Compliance Require?

A performance-based compliance submission typically includes:

Complete energy modeling simulation results
CF1R Certificate of Compliance documentation
Supporting mechanical, envelope, and lighting specifications
Registration through the CHEERS compliance registry (when required)

Our firm provides professional California Title 24 compliance services and detailed building energy modeling services to support permit-ready documentation.

We do not sell compliance software. We provide consulting and modeling expertise to prepare, validate, and submit accurate compliance documentation on behalf of project teams.

Which Path Is Better?

The Prescriptive Path works well for straightforward projects that easily meet code tables.

The Performance Path is often preferable for:

Custom residential designs
Multifamily developments
Commercial projects
Projects optimizing glazing, HVAC, or renewable integration

Because it evaluates total building performance, energy modeling enables greater architectural flexibility while maintaining compliance integrity.

Official References

LEED Certification Challenges for México

Wed, 23 Jun 2021 21:32:54 GMT

Mexico has long been a leader in LEED certification, it was recognized in 2019 to be the 8th country in gross square meter LEED certified projects[1] and has certified 232 projects since then (December 2020 to July 2021)[2]. It has been recognized to be a driver of increased rent/sale value, energy consumption savings, reduce maintenance cost, occupants comfort and to be environmentally friendly[3]. The importance of green building certifications, where LEED is the most applied worldwide, is to follow a holistic guideline and have weight the compliance from a recognized third party.

Image courtesy of USGBC[2]. LEED®, and its related logo, is a trademark owned by the U.S. Green Building Council®

Considering these factors why there is not more projects develop in our country? We believe it’s because of:

Lack of information or misinformation; and
Sustainability construction standards are deficient.

According to the Dodge Data & Analytics survey from 2018, 19% of the projects are pursuing green building activity based on client request, most of these clients are large companies that to comply with such certifications is at the center of their policies or that they take advantage of stock market green bonds or similar financial tools. Simplified, the certification allows the company to prove to their investors that their investment is environmentally responsible and in the long term generate more profit.

However, for smaller development there is 2 line of thinking: it is as simple as having few solar panels or it is too expensive. First, the LEED certification is not a perfect model but is accessible and touch all main sustainability branches: dense urbanization, urban mobility, fauna/flora conservation, material life-cycle, energy use, human comfort, and society impacts. We recommend you take a look at our LEED page for more details. Second, certification fees, credit documentation, and additional investment for building compliance are added cost but the process provides benefits that extend for the whole life of the building and is recuperated in 2-5 years of operation[4]. It is all a balance that developers and building operators should understand that the increase of 5-10% in sale value is a warranty that the construction will save energy, water, benefit the society.

The second factor to consider for LEED or green building certifications is that in most Latin American countries the minimum construction standards/practices are lacking to protect the environment or are not always followed. This means that following the best international practices and comparing to the latest international standard is a big leap for architect, engineers, and builders and this is reflected into costs that developer/investors are not planning. However, there is a learning curve and once reaching same construction sustainability standards as leading countries there is no higher investment required. Government are not leading the change as other topics are to prioritize such as poverty, healthcare, education, and security. Thus, it is crucial that the private sector lead the way to a healthier building environment.

Image courtesy of Dodge Data & Analytics - Smart Market Report 2018 [3].

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References:
[1] U.S. Green Building Council releases 2019 Top 10 Countries and Regions for LEED, https://gbci.org/us-green-building-council-releases-2019-top-10-countries-and-regions-leed
[2] Country Market Brief, https://www.usgbc.org/resources/country-market-brief
[3] World Green Building Trends 2018 Smart Market Report,
https://www.worldgbc.org/sites/default/files/World%20Green%20Building%20Trends%202018%20SMR%20FINAL%2010-11.pdf
[4] La certificación LEED, ¿se apaga en México?, https://obras.expansion.mx/soluciones/2015/07/10/la-certificacion-leed-se-apaga-en-mexico

Cogeneration Heating Power (CHP) Plant an energy efficient measure for cold countries.

Thu, 03 Dec 2020 22:40:21 GMT

One of the great approaches for cold climate countries to improve the efficiency in buildings where photovoltaic system could not be generate sufficiently, is through CHP (cogeneration of heat and power) plant.

How it works?

A CHP plant is a natural gas engine where the heat generated is extracted to heat fluid used in for room conditioning or domestic hot water use. The process consists in a boiler where the water passing boiling points is transferred to a steam turbine and make it rotate. This motion is then converted into electricity with a generator.

Why?

This approach for energy generation has been present for many years, but only recently the full potentials has been used. A steam turbine converts the energy from combustion with a rate of 40-50% of waste in heat, whereas the CHP use that heat to heat fluid for building usage losing less than 10%. These systems performance is increase which gives an efficiency of above 85% with and average distribution loss of 10% when used to heat district or cities. Traditional heating boiler have efficiency of 80% which is lower than the CHP and since the electricity normally cost more than natural gas per embed energy it is more than beneficial.

CHP Plant Schema - Courtesy of Pinterest*

Applications

There is various use of the CHP plant, but most of them are used where there is a large demand in heating such as cold countries where large plants produce the heat that is distributed to buildings just by connecting to the network. Additional to natural gas, the water could be heated from biomass or even landfill waste could be incinerated to be used in another form by people. The CHP could be used for campus, hospital, or industrial complex in order to be independent from the grid. Our team, have work on an industrial project in Mexico desiring to be self-sufficient in electricity even if heating is not required, however they have a 24h manufacturing cooled facility. Thus, the CHP heat is converted into chilled water for conditioning with an absorption chiller and the electricity produced helps reduce their consumption to 45% while lowering the maximum demand load number.

Modeling and LEED

Our energy modeler experts have documented various LEED projects that take advantage of CHP plant at local or district level. The preferred approach is to model the plant directly as a heating and electricity source, this is more than simple using IESVE. The information required are the efficiency curves, the network distribution loss, and the maximum heat output from the plant. This component is connected directly to the hot water loop, or chilled water loop when using absorption chiller, to provide the required heat at each second while generating energy. We highly recommend to model the CHP instead of manually inputting the contribution to your energy results, to be able to visualize CHP plant operation and how the electricity maximum load evolves.

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* CHP Technology, https://no.pinterest.com/pin/425027283577204903/

Net-Zero Home: Passive Cooling from Natural Ventilation

Fri, 27 Nov 2020 23:57:21 GMT

In a previous article - link - was presented a case study that highlighted the benefits offered by our net-zero consulting service which allowed a single-family project, designed by the environment friendly architectural firm OWN*, to save 52% in energy and provide 76% sDA, climate-based daylight calculation. In this article we will discuss a specific topic excluded from the previous one: natural ventilation for passive cooling.

Our client wanted to validate the possibility of natural ventilation cooling instead of mechanical, thus we identified that almost all days of the year around mid-day there is higher internal gain and solar gain. It was clear that there is a requirement in load and hours of operation for cooling and there could be savings in initial investment (equipment and installation) and energy saving (2%-5% annual energy consumption).

The method used to evaluate the design was to measure the thermal comfort (statistical person comfort considering temperature, radiation, humidity level, air velocity, clothing, and people activity). Our first evaluation considered the original design openings configuration (see left image below) which showed us that the natural ventilation cooling allows the living spaces to reach an acceptable comfort by reducing the apparent temperature 2-3 degrees Celsius. However, there was some undesirable hot spot (temperature of 30 degrees Celsius) which showed that even if on average space should be comfortable the ventilation is not sufficient. Thus, we proposed to take advantage of the modified design additional glazing, which provide better solar panel generation and increase daylight, to maximize the ventilation and natural cooling efficiency (see right image below).

Original Design

Optimized Design

The modified design with higher glazing on the south façade allows the fresh air to enter from lower level windows and escape from higher level windows after having cooled the spaces. The reason why this is more efficient than the original design is that the supply cool air has a greater distance from the escaping hot air. As well, there was added openings on the first-floor north façade which increase the suction of cool air from the ground floor which passed from the stairway and escape from the first-floor common corridor. Increased air flows from increased higher openings and the reduced mixing of supply/escape air by strategically placing high openings resulted in a reduction of apparent temperature of 1 degree Celsius and reduction of hot spots only to few wall surfaces. Below is presented the comparison for the 2 design of temperature distribution at 1.3m from finished floor of the two floors.

Initial Design - Ground floor temperature distribution from CFD.

Initial Design - 1st floor temperature distribution from CFD.

Optimized Design - Ground floor temperature distribution from CFD.

Optimized Design - 1st floor temperature distribution from CFD.

Finally, please take a look at the whole simulation results:

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* OWN, Architectural Firm with focus on balance between human and nature, www.thisisown.com/.

Net-Zero Energy Home: Case Study of energy modeling to reach 52% energy savings, high daylight and low glare.

Tue, 10 Nov 2020 20:12:04 GMT

The architecture industry is evolving to be more integrated and focusing on reduced energy consumption and increasing occupant comfort. Our team has worked closely with OWN*, Environment Friendly Mexican Architecture firm, to improve their latest single-family project at conceptual design phase. Our objectives were to reach Net-Zero Energy, maximize daylight while minimizing glare and take advantage of natural ventilation for passive cooling. We perform analysis using a building energy model and CFD simulations.

Original Design

Improved Design

The site climate requires to reduce heating consumption in particular during the night and reduce cooling consumption at mid-day. The temperature is reaching lower temperatures in January, but it is quite constant through the year since the project is located in the north tropical region. We thus would need to reduce slightly solar gain at summer when the sun is at its zenith, this was achieved by adding light shelves that are required to minimize glaring and increase daylight penetration.

The light shelves location to not interfere with glass door operation were placed above them, thus additional glazing was placed above the lights shelves. The additional glazing would also contribute, those openable, to increase the natural ventilation potential. However, the light shelves were not enough to reduce the glare enough, thus a glazing film that reduces the visual light transmittance to 17% in strategic locations. These strategies allow the increase in daylight from 34% sDA** to 76% sDA and reduce glare from 72% ASE*** to 25%ASE, all numbers are the weighted average for the occupied spaces.

Daylight Lux for ground floor: Left original design, right improved design.

Daylight Lux for 1st floor: Left original design, right improved design.

Glare compliance for ground floor: Left original design, right improved design.

Glare compliance for 1st floor: Left original design, right improved design.

To study the heating/cooling demand and energy consumption we develop a reference building which is based on the IECC-Mexico 2016 and the NOM-020-ENER-2011. Per the client request we use Autoclaved Cellular Concrete blocks with 51mm Polystyrene insulation, double glazing and UPVC window framing. The reduced consumption from these measures was only 17% compared to the IECC reference. Thus, we implement in addition the use of instantaneous water heaters, LED interior and exterior lighting, daylight and presence sensors, EnergyStar home appliances, and outdoor air supply with heat recovery. Combining these approaches we reach savings of 52% in yearly energy consumption compared to the reference building.

Monthly energy consumption per end-use: Left Original design and right Improved design.

Finally, the software used permits the evaluation of photovoltaic system generation. This guided the change of the first floor roof angle center location to increase the south-oriented area in order to accommodate more solar panels. The change allows the number of solar panels to be double which was required to reach the net-zero threshold we were looking for.
The roof change also opens a larger area in the north facade which benefits the natural ventilation performance. This would be discussed in a future article.

Please share your opinion below, your participation means a lot to us.

* OWN, Architectural Firm with focus on balance between human and nature, www.thisisown.com/.
** sDA: Spatial Daylight Autonomy, measure defined in standard IES LM-83-2012.
*** ASE: Annual Sunlight Exposure, measure defined in standard IES LM-83-2012.

From Business Values to Added Value – Tulum Real Estate Future

Thu, 14 Mar 2019 18:16:26 GMT

Tulum, Quintana Roo in Mexico is one of the most prized location for luxury and eco-friendly tourism. The demand and ROI for this city and the whole Riviera Maya region will keep growing and for real estate company to continue having success in the area the approach must change. Leader company of the industry (Los Amigos Tulum, GMB), business associations (COPARMEX Riviera Maya and ADIRM) and government institutions (General direction for Sustainable Tourism and Tulum City Hall) are already taking actions to push best practices among all players of the real estate industry. The key concept for all these people is sustainability, making our best to affect as less as possible the environment in the construction and operation of every real estate development.

For investors be sustainable means added cost which may not be possible to profit of it especially if the competition is not pursuing the eco-friendly path. However, a sustainable development sells better, faster, at a higher price, and is cheaper to operate. This does not consist only on installing solar panels; a sustainable building take advantage of natural light, has efficient material to reduce the need for cooling/heating the indoors, are equipped with water savings fixtures, and even recuperate gray water for toilets and landscape irrigation.

20% Premium for LEED-Certified Condos

To maximize the return of investment (ROI) for a sustainable development they must obtain recognition in the form of a certification. LEED (Leadership in Energy and Environmental Design) certification is one way to prove that a project is sustainable in all its aspects and is for any type of construction. Such certification is proven to reduce operation cost of at least 25% and people are willing to pay 20% more for LEED-certified condos. It has become a lot more than a fashion and is a growing must industry.

There is not LEED certified building in Tulum and few in the state (ADO Terminal Chetumal and CityExpress/Suites Playa del Carmen). Choosing to pursue a certification in all their project is for leaders who aims for recognition of their practices on a global level. Tulum is an eco-friendly destination which could grow bigger while staying green if the actors of the real estate industry incorporate LEED certification as the standard for the region.

Please share your opinion below, your participation means a lot to us.

Recommended additional content:
LEED Luxury home in Silicon Valley
World green building trends in technology
World green building trend in wellness

References:

The Challenge to Greener cities

Sat, 24 Nov 2018 18:00:37 GMT

There was a great progress in building sustainability and energy efficiency for the last 25 years[1]. The environmentalist and innovators are pushing this change from investors, to AEC[2] professionals and occupants. However, the goals they have set in mind is hardly reachable now: sustainability at city level. Newest, modern and high impact buildings are following the latest methods and technologies but small buildings, existing buildings, residential and non-residential consume a large amount of energy and generate more waste than they should.
Based on a survey from professionals of the industry in multiple countries we have identified the source:

Buildings must be designed/ built/ maintained/ and retro-fitted to reduce operating costs.

This is a paradigm shift from reducing initial cost to reducing the life-cycle cost of a construction. An increment of 5% to the initial investment of a building generate at least 25% reduction in operating cost. Considering the always increasing cost of utilities (water, electricity, and natural gas) and that most buildings lifespan is of 30 years, there is no doubt of the advantage of sustainability without talking about the benefits for our health and the planet.
Experts of the field are struggling everyday for this cause and are not satisfied with the results, the reasons why are:

Most Investors don’t want to invest more in a construction; and
Most Buyers/ renters are looking for lowest prices

Most people do not recognize the benefits of sustainability and energy efficient constructions. We believe that first steps to improve this are:

Educate masses about sustainability;
Promote sustainability as interdisciplinary goals for engineers and architects
Encourage construction workers to produce quality work
Enforce norms/ standards: some countries construction practices do not follow their standard for the benefit of reducing construction cost. This open doors to bad quality works and corruption (charging 2tons of insulation when only using 1ton).

Resulting from the global cultural change the construction investors would see that the market is asking for green buildings and will finance sustainable projects.

Special thanks to the various professionals whom share their opinions about the building industry challenges. This article launches a series of articles which aim to educate the masses about benefits of sustainability.

Please share your opinion below, your participation means a lot to us.

Recommended additional content:

References:

Definition for AEC, IMSCAD, http://www.imscadglobal.com/industries-AEC.php
Cover image, Eco-cities of the future, https://www.urenio.org/2011/01/31/sustainable-cities-oxymoron-or-the-shape-of-the-future/

[1] The U.S. Green Building Council was founded in 1993, it is a membership-based non-profit organization that promotes sustainability in building design, construction, and operation.
[2] The architecture, engineering and construction (AEC) industry consists of separate players who work together to bring a project to fruition.

Multiphysics at the concert room

Sun, 21 Oct 2018 19:09:31 GMT

Theatre of Epidaurus in Greece. Image courtesy of www.maxpixel.net.

Vertical sound propagation of Epidaurus theatre. T. Lokki, Acoustics of Epidaurus – Studies With Room Acoustics Modelling Methods.

Last week, I went to my local concert room to enjoy a great Chopin recital which inspired me to write this article. Most people enjoy the beautiful architecture of concert halls and the talent of professional artists from all fields without knowing the complex physics behind the building it take place. To make you understand the hard work of engineer and architects we made a list of the main goals behind a concert room design (in order of importance):

The shape of the concert room needs to ensure that the propagation of music, or sound waves, are not altered by other reflected waves or of reduced amplitudes. All spectators should enjoy the music in the way its intended, but also musicians on stage need to have a direct feedback to adjust their performance.
The walls need to be soundproof from exterior environmental noises and adjacent room’s concert sound.
Room occupants need to feel the indoor environment thermally comfortable. However, the challenge is into doing it for two different groups: calmly sited spectators and musicians under strong illumination.
HVAC systems have to distribute fresh air and keep the indoor at the required level of temperature, humidity, and oxygen. Since the rooms are large, air systems also must be large and they must be installed in such a way that their sounds are not altering the concert.

For many years, music halls and assembly rooms (such as lecture halls or churches) have been designed in a shoe-box shape and with luck provided a wonderful experience to the guest. Nowadays, the architecture aesthetics and originality are the main driver to such constructions. Thus, to maintain the aesthetics and succeed in the above 4 goals is quite difficult without a advanced simulations. Such problems require the simulation of all the physical phenomenon to be able to understand and optimize a concert room. How to simulate the above physics and combine them would be discussed in futures articles.

Also, it is important to mention that material selection is a major contributor to a well designed concert room since they can absorb or reflect sound waves.

Shoe-box shape concert room. T. Méndez, EDT, C 80 and G driven auditorium design.

We have prepared a space below for you to like this article, ask us more information, or simply to share with us your opinion. Your participation is our motivation to write every week.

Recommended additional content:

Future for Building Energy Modelling

Wed, 05 Sep 2018 07:00:00 GMT

Courtesy of Integrated Environmental Solutions Limited (IES).

On April 24, 2018, has been published the long-awaited ASHRAE Standard 209-2018, Energy Simulation Aided Design for Buildings except Low Rise Residential Buildings, which describes the most beneficial use of energy modeling for any constructions. I believe that it is a great reference for energy modeler however, it is not tomorrow that all projects will comply to this standard of using energy model to inform and optimize the design through 11 cycles from early concept to post-occupancy.

The importance of this movement is the message that experts wish to communicate to decision makers (general contractors, real estate firms, and investors) that an energy efficient building is designed with an integrative process which requires the involvement of a building energy modeler professional at all stages of the project, if possible.

The most probable outcome in the future years, as it has the bigger impact, would be that energy models are used in early phase of the project to define site information (location, orientation, shapes, height), then during the design process an accurate energy model would help HVAC engineers to choose/ optimize the systems to be installed. Finally, energy models would still be used to document compliance to standards such as ASHRAE 90.1 to obtain a green building certification

Few multinational companies understand the benefits of energy modeling-based optimization and this is a small investment compared to the efficient constructed building. For all construction industry professionals, ask yourself when you make your next project decisions: is it based on energy model analysis, or we always did it that way?

Energy Modeling in Architectural Design By Timothy L. Hemsath, Kaveh Alagheh Bandhosseini

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